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BADANIA I ROZWÓJ
dr inż. Zdzisław SALAMONOWICZ
dr inż. Wojciech JAROSZ
Szkoła Główna Służby Pożarniczej
ODŁAMKOWANIE PODCZAS WYBUCHU ZBIORNIKÓW Z LPG
Splinters forming during LPG tank explosion
Streszczenie
Działania ratownicze podczas zdarzeń z LPG wiążą się z wieloma zagrożeniami. Obecność zagrożeń zależy od sytuacji
na miejscu zdarzenia jak również od podjętych działań gaśniczych i ratowniczych. Umiejętność obserwacji i prognozowania
rozwoju sytuacji może zminimalizować ryzyko uszkodzenia i zniszczenia przyległych obiektów. Wcześnie podjęta decyzja
o ewakuacji i wycofaniu na bezpieczna odległość może uratować życie wielu ludzi i strażaków. W artykule zostały opisane
zagrożenia od odłamków powstających w trakcie wybuchu BLEVE. Opisano metodykę obliczania zasięgu odłamków powstających w trakcie wybuchów fizycznych zbiorników. Przedstawiono i omówiono wyniki eksperymentalnych wybuchów
11 kg zbiorników z LPG przeprowadzonych na poligonie. W większości przypadków typowa butla na „propan-butan” ulegała fragmentacji na kilka odłamków: w części cylindrycznej na 1-2 odłamki, dwie dennice oraz obręcz ochronną i zawór.
Średnio w trakcie wybuchu butli 11 kg z LPG powstaje od 4 do 6 odłamków. Zasięg odłamków zależy w głównej mierze
od kształtu i masy. Największe fragmenty przeleciały dystans około 70 m. Maksymalny zasięg rażenia odłamkami wynosił
około 250 i 270 m dla płaskich części poszycia oraz zwartych elementów butli. W niektórych przypadkach zasięg przewyższał maksymalny obliczony promień rażenia, prawdopodobnie ze względu na wystąpienie zjawiska „frisbee”. W trakcie
zdarzeń na otwartej przestrzeni Kierujący Działaniem Ratowniczym w sytuacji zagrożenia wybuchem 11 kg butli z propanem-butanem powinien wyznaczyć strefę niebezpieczna o promieniu nie mniejszym niż 300m.
Summary
The rescue operation during accidents with LPG vessels is connected with many threats. This threats depend from situation on
accident place as well as firefighting and rescue activities. Skill of observation and forecasting of situation development can
significantly minimise the risk of injury and destruction of objects. Early made decision about evacuation and withdrawal of
attendance on safe distance can save many occupants and firefighter lives. The threats from splinters forming during BLEVE
explosion was described in article. A method of calculating the range of fragments generated during physical explosions of tanks
was called. The results of proving ground experiments with 11 kg LPG tank were showed and discussed. In most cases those
type of vessels disrupt in cylindrical part of tank shell, which form few fragments of diversified shape and mass (1-2), two endcaps and gas cylinder top. Average number of missiles for cylindrical tank is between 4 and 6. The range of fragments depend
on shape and mass. The largest elements of tank could be found in distance 70 m from experimental position. Maximum range,
250 and 270 m, had flat pieces of tank shell and compact, small mass elements. In some cases maximum distance is longer than
calculated maximum range, because “frisbee” effect for flat parts can occur. Incident commander during action in open space
with typical 11 kg LPG tank, when exist high probability of explosion, should determine dangerous zone of at least 300 m.
Słowa kluczowe: LPG, odłamki, wybuch BLEVE
Keywords: LPG, splinters, missiles, BLEVE explosion
Introduction
The rescue operation during accidents with LPG vessels
is connected with many threats. This threats depend from
situation on accident place as well as firefighting and rescue activities. Depending on shape, size and type of breakdown, incident commander should consider during decision making process the possibility of:
• gas release to atmosphere and form of flammable vapour cloud with possibility of ignition mixture flammable gas - air,
• unconfined vapour cloud explosion (UVCE),
• jet fire (JF),
• boiling liquid expanding vapour explosion (BLEVE)
[Salamonowicz, 2009].
Secondary effects of BLEVE will moreover:
• blast wave,
• fireball,
• splinters.
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BADANIA I ROZWÓJ
Skill of observation and forecasting of situation development can significantly minimise the risk of injury and
destruction of objects. Early made decision about evacuation and withdrawal of attendance on safe distance can
save many occupants and firefighter lives. Therefore, what
distance is safe?
Theoretical
In majority BLEVE explosion is accompanied by blast
wave, fireball (flammable gases) and fly splinters. Dangerous zones for every above mentioned threats are appointive suitably from overpressure, radiant flux and kinetic
energy of missiles. Zone in which life or health risks occur is defined by range of splinters formed during BLEVE
explosion. Determination of zone in which overpressure
and heat flux cause specified injuries is not difficult and
is widely described in literature. Description of fragmentation and quantitative definition of danger zone is much
more difficult.
The results of BLEVE explosion, being sequence of
forming and spreading of splinters, depend from following factors:
• number and mass of splinters,
• velocity and range of missiles,
• direction of propagation of fragments,
• penetrative and destructive ability dependent on kinetic energy of splinters.
greater potential to bring damage [Hauptmanns, 2001]. The
number of splinters formed for cylindrical tank contains between two and fifteen and typically does not exceed five.
Holden and Reeves (1985) analyzed 27 BLEVE events
with cylindrical tanks. Four splinters were formed in 15%
of events, three – in 37%, two - in 30% and one missile in
26% of events. In case of cylindrical vessels, initial damage
usually follows in axial direction and tank is broken into
two fragments. If there are three missiles, tank can be divided into two end-cap and central body or first can be divided into two pieces, one end-cap and the rest, and then the
second projectile can be divided through the line between
liquid and vapour phase (Fig. 1). Lees (1996) analyzed 7
events with spherical tanks in which number of formed missiles contained between 3 and 19.
The total gas or vapour energy E inside pressure vessel is use up on formation blast wave and kinetic energy
of splinters, which were formed as a result of separation
individual elements from tank. For qualification of fragmentation effects accepts, then during BLEVE explosion
form 4 missiles. The kinetic energy calculation of splinters
is based on investigation, from which result that the coefficient of division of energy have value from 0,2 to 0,6
[Baum, 1988]. Therefore kinetic energy carries out:
E k = 0,6 ÷ 0.2 E
(1)
(p1 − p0 )V
(2)
E=
γ −1
Next, from kinetic energy and mass of splinters, initial velocity of fragments carried out:
1/ 2
where:
Fig. 1. General failure trend in cylindrical vessels
[Figas, 2001].
Ryc. 1. Ogólna tendencja fragmentacji zbiorników
cylindrycznych [Figas, 2001].
The number of missiles form from LPG vessels during
BLEVE explosion depends type of destruction, shape of
tank and energy of explosion. In general, vessel can disrupt
as fragile failure and ductile failure. Typically, BLEVE
will involve a ductile failure which will give less number
of fragments than if it were fragile failure [Baum, 1999].
However, missiles formed during ductile failure have much
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Ek
m
p0
p1
V
γ
vi
⎛ 2E ⎞
vi = ⎜ k ⎟
⎝ m ⎠
kinetic energy
total mass of the empty tank
ambient pressure outsider vessel
absolute pressure in vessel at failure
internal volume of tank
ratio of specific heat
initial missiles velocity
(3)
J
kg
Pa
Pa
m3
m s-1
The simplest relationship for calculating missiles rang is:
v sin (2α i )
R= i
g
2
(4)
where:
g
gravitational acceleration
m s-2
R
horizontal range
m
αI
initial angle between trajectory and horizon
initial missiles velocity
m s-1
vi
Splinters will travel on maximum distance when αi = 45°.
BADANIA I ROZWÓJ
2
Rmax
v
= i
g
(5)
The above mentioned equation does not include air
resistance coefficient. Some models include air resistance
to range calculation, for example Clancey model (1976):
R=
m1 / 3 v
ln
ka
u
where:
a
air resistance
k
empirical coefficient
mi
missiles mass
ui
end missiles velocity
vi
initial missiles velocity
(6)
(1,5 – 2,0)
(0,0014 – 0,002)
kg
m s-1
m s-1
In some accidents distances were unexpectly large.
Baum (1999, 2001) explain this phenomenon as „rocketing” effect. If vapour forming from evaporating liquid
remnant, escapes from open part of end-cap, then additional acceleration appears. This phenomenon is similar
to gas release from rocket’s nozzle and it increase maximum distance. In case of flat splinters, range of their flight
increases almost twice as the result of phenomenon called
„frisbee”.
Experimental
Sensors to measure temperature and pressure were installed
directly outside and inside tank. During experiments (heating to explosion) were measure temperature in vapour and
liquid phase and pressure inside tank. Heating was performed with use of constructed burner stand and mounted burner of approx. 20 kW power, used during roof works.
The figure below present experimental vessel with
sensor. Following parameters during investigation were
measured:
• temperature liquid and vapour phase inside vessel,
• pressure inside vessel,
• test time,
• temperature outside vessel,
• temperature of vessel wall,
• splinters mass,
• distances between splinters and central point,
• pressure of blast wave.
Part of this parameters like splinters mass, pressure inside tank, distance and tank volume are used in this paper.
Table below contain parameters our testing vessel.
Technical parameters of vessel
Table. 1.
Tabela. 1.
Parametry techniczne butli testowej
Parameter
Value
Capacity
27 dm3 (11 kg)
Height
595 mm
Diameter
300 mm
Thickness of tank shell
1,9 mm
Material of tank shell
StE 355 DIN 17102
Maximum service pressure
2,5 MPa
Results and discussion
Carried out experiments show, that during BLEVE explosion, pressure vessel cracks into 5-6 parts (3-5 main missiles and few smaller fragments). All tanks were disrupt in
similar way. In each case gas cylinder top with thread and
two elliptic end-caps (heads) of vessel were ripped off.
Whereat the upper part of tank break off with considerable
fragment of tank shell. Rest of tank shells formed 2 or 3
splinters. The direction and range of missiles was showed
on figure 1 and 2. Pressure inside tanks before explosions
were 42 bar and 72 bar.
The range of fragments depend on shape and mass.
The largest elements of tank could be found in distance
70 m from experimental position. Maximum range, 250
and 270 m, had flat pieces of tank shell and compact,
small mass elements (e.g. head on Fig. 3 and small piece
on Fig. 4).
Fig. 2. Diagram of vessel with measuring sensors.
Ryc. 2. Zbiornik testowy z sensorami pomiarowymi.
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BADANIA I ROZWÓJ
Table. 3.
Splinters and range – 2.
Tabela. 3.
Odłamki i zasięgi – 2.
Nb.
Splinter
Range
[m]
Mass
[kg]
Theoretical
max. range
[m]1
1
main part of the
tank shell
44
5,68
34
2
down head
142
1,61
119
3
up head
154
2,37
81
4
safety collar
153
0,54
356
5
gas cylinder top
244
1,38
139
Fig. 3. Direction and range of missiles from LPG
tank explosion – 1.
Ryc. 3. Kierunek i zasięg odłamków po wybuchu z
biornika z LPG – 1.
Splinters and range – 1.
Odłamki i zasięgi – 1.
Nb.
1
1)
Splinter
part of the tank shell
Table. 2.
Tabela. 2.
Range
[m]
Mass
[kg]
Theoretical max.
range [m]1
122
2,34
49
2
safety collar
79
0,89
129
3
up head
91
2,10
55
4
down head
78
1,55
74
5
gas \cylinder top
143
1,36
84
6
flat part of the tank
shell
257
1,86
62
Fig. 5. Gas cylinder top with sensor outlet after explosion.
Ryc. 5. Głowica załadunkowa
z czujnikami pomiarowymi po wybuchu.
– from eq. (5); Ek=0,6E
Fig. 6. Safety collar after explosion.
Ryc. 6. Obręcz ochronna po wybuchu.
Fig. 4. Direction and range of missiles from LPG
tank explosion – 2.
Ryc. 4. Kierunek i zasięg odłamków po wybuchu
zbiornika z LPG – 2.
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Fig. 7. Down head after explosion.
Ryc. 7. Dolna dennica po wybuchu.
BADANIA I ROZWÓJ
Conclusions
The number of missiles formed during BLEVE explosion, as well as during other explosions, is impossible
to foresee. All calculations and forecasts are based on
statistical data, since main source of information about
fragmentation is historical data assembled during many
years.
However analysis of 11 kg cylindrical vessels splinters shows some regularities. In most cases those type of
vessels disrupt in cylindrical part of tank shell, which form
few fragments of diversified shape and mass (1-2), two
end-caps and gas cylinder top. Average number of missiles for cylindrical tank is between 4 and 6.
In some cases maximum distance is longer than calculated from eq. 5, because “frisbee” effect for flat parts
can occur.
Incident commander during action in open space with
typical 11 kg LPG tank, when exist high probability of explosion, should determine dangerous zone of at least 300 m.
References
1. Baum, M.R. (1988). Disruptive Failure pf Pressure
Vessel: Preliminary Design Guidelines for Fragment
Velocity and the Entent of the Hazard Zone. Journal
of Pressure Vessel Technology, transaction of the
ASME, 110, 168-176;
2. Baum, M.R. (1999). Failure of a Horizontal Pressure
Vessel Containing a High Temperature Liquid: the Velocity of End-cap and Rocket Misssiles. Journal of Loss
Prevention in the Process Industries, 12, 137-145;
3. Baum M.R. (2001). The velocity of large missiles
from Arial rupture of gas pressurized cylindrical vessels. Journal of Loss Prevention in the Process Industries, 14, 199-203;
4. Clansey V.J. (1976). Liquid and vapour emission
and dispersion, in: Course on Loss Prevention in the
Process Industries. Department of Chemical Engineering, Loughborough University of Technology;
5. Gubinelli G., Zanelli S., Cozzani V. (2004). A simplified model for the assessment of the impact probability of fragments. Journal of Hazardous Materials,
116, 175-187;
6. Hauptmanns U. (2001). A procedure for analyzing
the flight of missiles from explosions of cylindrical
vessels. Journal of Loss Prevention in the Process Industries, 14, 394-402;
7. Figas, M. (2001). The Handbook of Hazardous Materials Spills Technology. McGraw-Hill, New York;
8. Holden, P.L., Reeves, A.B. (1985). Fragment hazards
from failures of pressurized liquified vessels. Chem.
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Industries – Hazard Identification, Assessment, and
Control, 1-3, Butterworth-Heinemann, Oxford;
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containing containers, Polski Przegląd Medycyny
Lotniczej, 15/1 (2009) 51-59;
st. kpt. dr inż. Zdzisław Salamonowicz
ukończył Szkołę Główną Służby Pożarniczej w 2003 roku
i uzyskał tytuł magistra inżyniera pożarnictwa w zakresie inżynierii bezpieczeństwa pożarowego. W 2005 roku
ukończył studia na Wydziale Chemii Politechniki Warszawskiej z dyplomem inżyniera na kierunku technologia
chemiczna, specjalność – materiały wysokoenergetyczne
i bezpieczeństwo procesów chemicznych. W 2011 roku,
na Wydziale Inżynierii Procesowej i Ochrony Środowiska
Politechniki Łódzkiej otrzymał tytuł doktora nauk technicznych w zakresie inżynierii chemicznej, specjalność bezpieczeństwo procesowe. Obecnie pełni służbę w Szkole Głównej Służby Pożarniczej jako kierownik Zakładu
Ratownictwa Chemicznego i Ekologicznego na Wydziale
Inżynierii Bezpieczeństwa Pożarowego.
bryg. dr inż. Wojciech Jarosz
jest oficerem PSP. W 1993 r. ukończył Szkołę Główną Służby Pożarniczej W Warszawie. W 2006 r. obronił
doktorat Zagrożenia środowiska naturalnego powodowane przez zjawiska wykipienia i wyrzutu paliw w czasie
pożarów zbiorników zawierających ciecze ropopochodne
na Wydziale Inżynierii Środowiska Politechniki Warszawskiej. Od 1993 r. pracuje w Szkole Głównej Służby Pożarniczej zajmując kolejno stanowiska asystent, kierownik pracowni, adiunkt, prodziekan. Obszar zainteresowań
naukowych to zagrożenia związane z materiałami niebezpiecznymi, szczególnie z ciekłymi węglowodorami oraz
zagrożenia procesowe.
Recenzenci
dr inż. Adam Majka
dr inż. Tadeusz Terlikowski, prof. nadzw.
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